Brake assembly



Jall- 1935. c. A. SAWTELLE r-:r AL 1,

BRAKE AS SEMBLY Filed May 26, 1930 2 Sheets-Shetl fig.b.

INVENTORS' Jan. 1, 1935'. c. A.- SAWTELLE. El AL 1,935,953

' BRAKE ASSEMBLY Filed May 26, 1930 2 Sheets-Sheet 2 firmmfljarmsta etter ATTORN EY,.S'

#W mmwmwm *"I'he invention relates to brake mechanisms of tha t type {in "wlflchfthe brake shoe or other brake apblyj'ng me'mber has'a'portion' of its trio tion surface-which tends 'to wrap or cling '{to '5 the co ooeraltin'g surface of- 'the=drum and another portion whi'ch tends to unwrap or herepelld -Irorri the drum'if'It is the object of' the present invention t6 provide automatic nreans for utilizing the wrapping force of the one portion I or 1 operating the unwrapping force in the other portio'n so as to more nearly'equalize uthe brakingemciency of these two portions;- "Itls e 'a further object to so proportionfthese op'bosing forceslthat there' will be 'preponderenceiof the "2s construction 1 as hereinafter set tort ping portions ot the brake; ii;

wrapping forceytherebyj making the brake to certain extent self-energizing. Inasmuch; however-g'as brak'es areused durin'g-reversedrlving' l as well as "forward driving and asfthe 'wrflppin and unwrapping portions are-reversed in'l'unotion during such u'se it is Jar further' object" of the invention ft'of efiect a n eutomatief shifting of leverage so as to have a repdnaemncegor the wrapping f force in the l reverse driving: as well as for' -forward hdri vingy With these and mother "obj e'cts -in view the invention consists i ;*:F1gure '1 is a side elevfition ofthe breikelmech janjsni r3ivp Figure-2-is -an v I nectinglink betweenthe wrapping and 'unwrapvFigur'e 3 a' eross sectiom showing theisoperate ing mechanism in elevation; 1 =Figure 4 is ia, cross' section 'on line of disk" adjecent 'to "sgid-drumfi 1s 5 an internal 'brakellsho'e or 'band arranged-within the andextending around the greater portioimi the circumference --thereof.'{ ll're free ends" of this shoe are connected to eelch other by a floating linkagei 'thro'ugh which" the 7 shoe mas pended 31111170 frictional contact with the 'drum crankafshaiving 'a. iulcrum 'portion 'apd the arms E and E? extending therefrom at --substanend elevationshowing the cona lseotionalview on me e is brelke-drumbf eny suit-f able 'construction and' B is' he" brak head or Dal-ms taet tei',

e 1 na-1s pivdta1'1y 1 connected at H to ithe -breke head B. In .addition to the armsn Ei find E the lever E is pror- 'videdjfwith en 111 stameactuatin arml' l wh'ich fportion "Thusin" retionlt "11:13 any outwar nd" th .e

and-15" to retrejo'tithe brake Hosa'hd one provided wgmme gfg 4 mm "the brake-{ r m and ma am;

the braking surface said means being of the following construction:

' S and S" are bars extending in alignment with each other and slidably attached to the head B by bearing clips T. The outer ends of these bars extend into proximity to portions of the'hrake shoe .on oppositesidesoi the center thereof tifllldf mm atop! for limiting the radial inward movement or "the shoe at these "points.

opposite directions to compensate for any wear in the brake lining.

Y carried by the brake band and at th'eother end to .a bracket 2 carried by the backing -.pl ate B. spring 082$. tohold the band against displacement with reference to ather-plate 13.; a

. .1.-the p rts a e o er iw dgth brake shoe 0 will qbe -held with its braking suriace slightly outof contact with the brake drum; A and concentric thereto, Tosetthe brake th reek- 3 i tu e -w ui abl pedal .oonnections5not shown) so es to cause the. roller R; to press arm 1 radially. inward. This will turn .the-biiurcated member .E around the fulcr m pit ot.Ff, swinging inward arm E and thereby; actuating the arm M oithe man e ;M.-; r p as a s r d n toggle, Whi Se he ends of .the .-shoeii7o1n "each other and enlarge the diameterthereoi so as. to; come, into .iriction contact w the n e s e o t sinning that the drumisrotating in the direction of" the arrow 5, .f-riction'with the" surfaceiofr the shoe. to; rotate the latter, and as the toggle linkage a limited amount ,of such-movement is permitted by the swinging of the G and N. However, the moyementlof the N a re'stedby tonracr with the stop e s w n. movement. a the linkage in the direction oiIthe'arro-m,

I"heir' tiionoithe un ron portion of the brake adjacent toth'e eye' bracketD will tend to swingtheshoe sons to itslbraking pressure or; will causelit ito-wrap.fas it'is technically known .lfhisiorce without. restraint mightdevelop an objectionably hi h pressure either the skidding of r the wheels or destrnctive wear of theliningat this point.- .pn the other the; portion or the brake l'shoe adjacent to; the evebracket 1) would berepelled by: the friction contact with the so {as to lose its eiiicienc'y. Both of these. eilects are. modified'by the connecting'linkagaas' any movementof lever E by thewrapping, force of portion 'of. 'shoe (will cause a corresponding. movement-of the letter N tending to f once a portionof the shoe attached-there, to intodinner braking contact withthe drum; This in; turn; will increase the -unwrapping force dr to co n r t w ap i for If the leversEandNwere aural the-two forces ou d m ants e hi tb r u r -ab ve s t it is one of the objects of the invention to produce hawkenergizing brake which will assist the manualiorce .actuaitingthe lever- I. This ing of the arms E and M and the levers E and M which develops a preponderance of pressure by the wrapping portion over the counterpressure by the unwrapping portion.

When the brake drum is rotated in a reverse direction as indicated by the arrow 6, the portion. oftl e shoe which iormerlyjhec wrappin 1 3 9 1; wi l n 'i b 'i n w pp n force while the portion which was" formerly the wunwrapping portion will develop a wrapping force. This would not, however, produce the .same braking action in reverse as in the forward rotation of the drum, as the unwrapping force would'bein preponderance, thereby not only dexstroying'thelselfenergizing feature but requiring additional manualipressure to counteract the g unwrapping force. Such a result is avoided by The reference character x iseeEigme'dti iiidicates a spring attached at one end .to aistudv changing -the* leverage of the linkage which is automatically accomplished by the limited romoon of the entire system on the reversal of the'dru m. As, has beenstated; the stop Ouresists rotation of the system when the drum is rotating inta forward direction but will ,have no eifeet in resisting a -reverse rotation. 'It has also beenstated that thestop 0 :is during the forward rotationof the gdrum separated vfrom the lever As soonghowever, asthe direction of -the drum is vreversedthe whole system will rotate untilrthe leverE comes in. contact with the stopO' which :thenoperatesas an anchorage to :prevent iurther'movement; This will change the :fulcrum of the leverE fromathe pin F- to the stop 0, .shorteningxthe armyE- v and lengthening the arm E 'This will change-the leverage sufficiently to develop a preponderance of pressure by the wrapping portion of the brake adjacent to the eye bracket 13' and :willxtherefore render the brake self-energizing 'm reverse as well as in forward direction.

-Whatwe claim as oun-iinventionriszw 1.3m abrake mechanism including a rotating element andaabrake element for enga in the same havinga wrappingrportion and an unwrapping; portion;- =;ot anlinka'ge; between said wrapping and unwrapping portions for opposing the wrapping ,force topthejunwrapping force and proportioned to give a preponderance ,ofpressure by. the wrappingiforce when therotating element is rotating in one direction, andzmeans automatically operating upon the rotation. of said element in the oppositedimction for changing said linkage to obtain a. preponderance of pressure by the wrapping torcein' this direction also. 1: .21. v 2.- Ina brake mechanism, the combination with a rotating drum, of an internal brake ale-'- menttherein having apwrappin Portion and an unwrapping portion, a floating linkage between said wrapping andunwrapping portionsthrough which the wrapping force is opposedz o the unwrappin f rce, manually operable. means ior expanding said: linkage to -.more said element into braking contact with the drum, a {stop for limiting-movement ofsaid floating-linkage and element when'the drum risrotatingin one direction, a'second stop forlimiting the floating movement of saidglinka'ge and element when the drum is rotated in the reverse vedirection and means cooperat-ing.-'withsaid stops'ior. changing the leverage in saidlinkage whenrsaid-drum 'rotated in a reverse directions to secure a: preponderance of wrappingjorcein each direction.

.3. In a. brake: mechanism, the combination with a rotatingdrumof-an internal brake element therein haying-a wrapping portion and an 1,985,968 unwrapping portion, a linkage between said wrapping and unwrapping portion including tog gle levers, manually operable means for actuating said toggle levers to expand saidelement into braking contact with the drum, co-operating elements in said linkage for opposing the. wrapping force to the unwrapping force with a preponderance of pressure in favor of the wrapping force when said drum is rotating in, its forward direction, a stop for engaging said linkagel to anchor said element when said drum is rotated g in its forward direction, a second stop for engaging said linkage toanchor said element when the drum is rotated in reverse direction,said

second stop being located to change the leverage of said linkage so as to givea preponderance of the wrapping force in this direction also.

4. In a brake mechanism, the combination with a rotating brake drum and a stationary brake!" head, of an internal brake element within said drum having a wrapping portion and an unwrapping portion, a floating linkage between said wrapping portion and unwrapping portion through which the force developed by the one is opposed to that developed by the other, said linkage including a pair of bell crank levers respectively pivotally attached to said portions, and having arms of unequal length connected to each other constituting toggle links and also an increase in power leverage between said wrapping portion and unwrapping portion, swinging links mounted on said brake head to which said bell crank levers are fulcrumed, a stop for arresting movement of one of said links when said drum is rotating in forward direction, an arm for actuat-V ing one of said bell crank levers to straighten said toggle links and to expand said element into braking contact'with said drum, and a second stop for arresting movement of said linkage scribed. v i a 5. In a brake mechanism, a brake 'drum," a stationary backing plate, a brake element engaging said drum,.and having spaced ends, interconnecting linkage forthe said ends comprising bell cranks of "unequal ilength having one arm of each bell crank pivotally connected to one another to form leversio'f fixed length, the'other 1 arm of each bell crank being connected respectively to the ends of the brakeelement, and link [members pivotally mounted on said backing plate and'respectively pivotally' supporting said 15 bell cranks;;lwh'ereby .said bell crank pivots shift upon operation of the bell cranks.

* 6'. In a brakemechani'sm, a rotating member, floating friction means engageable with said member and having a wrapping portion andan unwrapping portion, floating linkage between,

said wrapping portion and unwrapping portion for opposing the wrapping force to the unwrapping force and proportioned to give a preponderance of pressure by the wrapping force when said member is rotating in one direction; i

7. In a brake mechanism, a rotating member,

- a brake element for engaging said member having a wrapping portion and an unwrapping por:

tion, an anchor for the-brake element when said member is rotatingin one direction, and floating linkage between said wrapping and unwrapping portions cooperating with the anchor for 1 opposing the wrapping force to the-unwrapping force and proportioned to give a preponderance of pressure by the wrapping force. v

CHARLES A. saw'rnm'n. ARMlN A. DARMS'I'AETIER. 

